Air Blast System for Blast Furnace A blast furnace (BF) produces liquid iron (hot metal) by the reduction of ore burden with reducing gases. The reducing gases are produced by the reaction of oxygen with coke and coal. This oxygen is part of enriched hot air blast which is blown and distributed at the bottom of the BF through the straight pipes, blowpipes and the tuyeres. This set is connected to the main bustle pipe. The volume of air which is enriched with oxygen and blown for the process in the BF to take place is provided by the air blowers. These air blowers take the air from atmosphere and compress it to the required pressure. This compressed air which is at about up to 200 deg C temperatures after compression is enriched with oxygen and blown into the hot stoves where the temperature is raised up to 1.200 to 1250 deg C. This hot blast air is then taken to bustle pipe through hot blast main. Air blast systems of modern high capacity blast furnaces operate with blast temperatures of up to 1350 deg C and blast pressures up to 5 kg/sq cm (g). The whole process is typically shown in Fig 1. Fig 1 Schematics of typical air blast system The main components of an air blast system of a blast furnace consist of (i) air blower, (ii) cold blast main, (iii) hot blast stove along with its combustion system, (iv) hot blast main, (v) bustle pipe, (vi) blow pipes and tuyeres known as tuyere stocks, (vii) set of valves, and (viii) control instruments. The air blower is the first equipment in the air blast system. It is located in the blower house and is meant for providing cold air blast to the...

The Process of Blowing-in of a Blast Furnace The process of starting a blast furnace after its construction or after its relining is called blowing-in. The blowing-in process is carried out in several steps (Fig 1) which consist of (i) drying out the lining, (ii) filling of the blast furnace with a specially arranged high coke blow-in furnace charge, (iii) igniting of the coke or lighting of the blast furnace, and (iv) gradually increasing the hot blast (wind rate) with frequent castings to ensure the raising of temperature of the blast furnace hearth. During the period of blow-in, the burden ratio (ratio of the ore to coke) is adjusted according to a predetermined schedule until the normal operation of the blast furnace is achieved and the blast furnace starts producing the normal quality of the hot metal. Fig 1 Steps in the blowing-in process of a blast furnace Newly constructed or relined blast furnace is to be carefully dried before the coke is ignited. It is because the large amount of water contained in the slurry used for refractory brick laying and the water absorbed by the refractory brick work is to be driven off as much as possible for avoiding extreme thermal shock. There is sufficient data available that blowing-in of a blast furnace can cause damage to the refractory lining even when it has been properly dried. Furthermore, if the water from these sources is not removed from the blast furnace before it is put into operation, it absorbs heat more than that provided for the blow-in charge and hence prevents the hearth from reaching the desired temperature. In such cases, hot metal and liquid slag entering the hearth can freeze there and in such case it becomes impossible to remove them...